In the past, typical completions would involve a casing which is run in the wellbore and cemented. The wellbore thereafter is extended and a casing or liner is suspended to the uphole casing which had earlier been cemented. Typically, liner hangers were used to suspend the lowermost portion of the casing or liner which is added, generally in a deviated wellbore. These lower casings typically involve the use of openings or slots extending into the horizontal segment of the wellbore. Typically, the slotted casing or liner was run with external packers; hence, the term ECP (external casing packer). In view of the openings or slots in the liner supporting the ECPs, internal mud or cement pressure could not be used within such liners to inflate the ECPs disposed along the length of the liner. Instead, each ECP had to be isolated so that it could then be actuated to expand into contact with the wellbore, isolating the desired zones of slotted casing. Prior designs have been developed to isolate each specific ECP and allow it to be inflated with mud or cement. Such prior designs are illustrated in U.S. Pat. No. 5,082,062. This patent, entitled "Horizontal Inflatable Tool," refers to a tool manufactured by CTC Corporation of Houston, Tex. This tool involved a concept of isolation of an ECP, using an inner workstring, followed by a series of mechanical operations to begin the inflating operation. The problem with prior design tools is that in deviated wellbores, it is difficult to communicate mechanical movement from the surface and know that, reliably, such movement has been translated to an equal amount or degree of movement at the desired location. Hence, the prior systems added a degree of unreliability to the inflation procedure for the ECPs, thus creating uncertainty as to whether each of the ECPs, as desired, had been fully inflated.
The apparatus and method of the present invention provide greater reliability in knowing that the ECP has been properly inflated. Reliability is further enhanced by the hydraulic rather than mechanical operation. Reliability is built into the system through a variety of features which ensure, through pressure-equalizing techniques, the longevity of the seals around the opening for each ECP. Additionally, a provision has been made to allow removal of any excess cement by a reversing procedure. Finally, to minimize the effort required to remove the inflating tool out of the hole, other relief provisions have been incorporated into the design to facilitate pulling out of the hole.